silly and lazy
Not really, if you think about how many distros there are and how many people are currently wasting time with re-packaging software over and over for them i think you'll come to realize that this is a very clever and efficient move. The way it is done currently seems rather silly in comparison.
Sidenote: You keep using the term OS ... which is false in the sense, that flatpak doenst come with a direct hardware layer / kernel